The Birth and Death of Our Solar System: An Interview with Konstantin Batygin

Konstantin Batygin recently joined the Caltech faculty as assistant professor of planetary science, following graduate school at Caltech (PhD '12) and a postdoc at the Harvard-Smithsonian Center for Astrophysics. Batygin was born in Moscow, attended elementary and middle school outside Tokyo, and moved to San Jose while in high school. He chose UC Santa Cruz for college to be near the beach and to continue playing with the band he had formed in high school. He decided to major in astrophysics the day before classes started his freshman year.

It's a decision Batygin has never regretted. Early in his undergraduate career, a mentor started Batygin thinking about the fate of our solar system. From there, one question led to another and another, and now Batygin works on everything from the evolution of our solar system to the weather on exoplanets.

Batygin recently spoke about the string of synchronicities that brought him to planetary astrophysics and to Caltech.

How did you find your way into astrophysics and planetary science?

I applied to UC Santa Cruz as an engineering major. On registration day, I had to go pick up a piece of paper from some office, and there was a guy there. I don't know if he was a student or what. But he said to me, "Yo dawg, what's your major?" I told him it was engineering. And he said, "You should do astrophysics. It's dope." As I left the office, I thought, "Wow, astrophysics does sound totally dope." So I went to the physics department and changed my major.

When did you develop an interest in planetary science?

Planetary science wasn't in my plan. I wanted to do high-energy astrophysics. But then at a department party I met Greg Laughlin, a planetary scientist at UC Santa Cruz. He's a very creative guy and an expert in chaos theory. He suggested that we might try to figure out what the long-term fate of our solar system would be. I thought to myself, "Surely someone like Newton must have solved that problem already." But I was wrong about that. As soon as we started working on this stuff, I just fell in love with it. It's a very counterintuitive situation. You tend to think that the motion of the planets is like clockwork, where things keep going around in an orderly fashion. You only need one physics law—gravity—to predict the basic motions of the planets. But it's actually a very complicated problem.

In what way?

Part of it is pretty easy. For the numerical simulations involved, any reasonably astute graduate student could do the work. The more difficult part of the problem is trying to explain what we find in the numerical simulations. For example, the simulations reveal that if you wait long enough, Mercury will leave the solar system. It will become unstable, its orbit will become unbound, and it will take off.

Really? Even though it's the closest planet to the sun, it just flies off rather than falling into the sun?

Yes. It's called chaotic diffusion. This happens over a multibillion-year timescale. Planetary orbits are a little bit like weather. We can't predict the weather for longer than three days. But we can generally expect that the weather is not going to change by thousands of degrees; it's going to be in some bounded range. Planetary orbits are like that. They vary, but they mostly hang out in a well-defined region of phase space. Occasionally, though, they leave that phase space and transition into a different shape. This is why Mercury takes off at some point in the future. It's a beautiful problem. You've got eight members of the system—planets—whose masses are low. But over long time spans, they exchange angular momentum in a deterministic yet unpredictable manner. If you wait long enough, at one point Mercury bites off more angular momentum deficit than it can chew and leaves the solar system.

Why did you choose Caltech for graduate school?

First I got an email from Mike Brown [Caltech's Richard and Barbara Rosenberg Professor and professor of planetary astronomy], saying congratulations, I had been admitted to Caltech. I thought, "Well, this is a funny coincidence, another Mike Brown." Then I realized, "Wait, this is the Mike Brown!" So I came to campus, just for a day, but I immediately knew this was where I would come for graduate school. I have never felt quite as at home as I do at Caltech. That's been true from the first moment.

Why do you think you had such an instant affinity for Caltech?

Southern California is pretty awesome, so there's that. But I think Caltech has a unique aura, and I think that has to do with quality. It is the pursuit of quality rather than quantity, so to speak. And that's basically why we do science.

Had you completed your work on the long-term fate of our solar system before you came to Caltech for grad school?

Yes, but I've actually gone back and revisited that problem. We've tried to put ourselves in a time before computers were around, and ask what we learn about orbits in our solar system if we don't assume that everything works like a clock, to ask if we can get at the numerically obtained results with perturbation theory. We're hoping to proceed entirely analytically, getting to the underlying physical structure of dynamic instability.

Newton was working with an assumption of clockwork motion?

No, when Newton came out with his law, he himself didn't believe that the solar system would be stable. He believed that gravity would gradually unravel it, and that God would have to come in and reset it. The idea of perfect determinism was introduced later by Laplace, among others. We're seeing the same instability, but looking at secular solutions to the problem of what happens to the solar system over time.

What are you working on now?

In effect I'm continuing all the projects that I've started up until now. When I came to Caltech as a grad student I was pretty comfortable with working on the dynamics of the solar system. But then Dave Stevenson [the Marvin L. Goldberger Professor of Planetary Science] shattered my world by opening up a whole set of other interesting problems in planetary science. And Mike Brown and I worked on the solar system, but we examined the beginning rather than the end. The early evolution of the solar system is also very wild and chaos-dominated. I also ended up working on the interiors of exoplanets and the formation of the Kuiper belt, and at Harvard I worked on the evolution of protoplanetary disks and the weather on exoplanets.

Do you observe the planets directly, or do you use other people's observations?

No, I don't observe. I should not be allowed near a telescope. I have great respect for observers, but it doesn't come naturally for me. You have to be really focused. I don't have observing capabilities.

Have you found a band to play with since you got back from your postdoc in the Boston area?

Yes, my band, the Seventh Season, keeps remaking itself. You can find our music on iTunes. Once in a while we get a check from iTunes for $20 or so. We're working on two new albums now. They're untitled. We're open to suggestions.

And do you still like the beach?

I haven't been surfing yet, but we went to the beach last weekend. My daughter loved the water. It was a scandal when I tried to take her out after an hour in the ocean.

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Cynthia Eller
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The Birth and Death of Our Solar System
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Looking Forward to 2020 . . . on Mars

A Q&A With Project Scientist Ken Farley

While the Curiosity rover continues to interrogate Gale Crater on Mars, planning is well under way for its successor—another rover that is currently referred to as Mars 2020. The new robotic explorer, scheduled to launch in 2020, will use much of the same technology (even some of the spare parts Curiosity left behind on Earth) to get to the Red Planet. Once there, it will pursue a new set of scientific objectives including the careful collection and storage (referred to as "caching") of compelling samples that might one day be returned to Earth by a future mission. Today, NASA announced the selection of seven scientific instruments that Mars 2020 will carry with it to Mars.

Ken Farley, Caltech's W.M. Keck Foundation Professor of Geochemistry and chair of the Division of Geological and Planetary Sciences, is serving as project scientist for Mars 2020. We recently sat down with him to talk about the mission and his new role.

 

Congratulations on being selected project scientist for this exciting mission. For those of us who do not know exactly what a project scientist does, can you give us a little overview of the job?

Sure. Conveniently, NASA has a definition, which says that the project scientist is responsible for the overall scientific success of the mission. That's a pretty concise explanation, but it encompasses a lot. My main duty thus far has been helping to define the science needs for equipment that we are going to send to Mars. So while we haven't actually done any science yet, we have had to make a lot of design decisions that are related to the science.

The easiest place to illustrate this is in the discussion of what is necessary, from the science point of view, in terms of the samples that we will cache. We have to consider things like how much mass we need to bring back, what kind of magnetic fields and temperatures the samples are going to be exposed to, and how much contamination of different chemical constituents we can allow. Every one of those questions drives a design decision in how you build the drilling system and the caching system. And if you get those wrong, there's nothing you can do. So there's a lot of thought that has to be put into that, and I convey a lot of that information to the engineers.

Now that we have a science team, I will be helping to facilitate all of its investigations and helping the members to work as a team. MSL [the Mars Science Laboratory, Curiosity's mission] is demonstrating how you have to operate when you have a complex tool (a rover) and a bunch of sensors, and every day you have to figure out what you're going to do to further science. The team has to pull together, pool all of its information, and come up with a plan, so an important part of my job will be figuring out how to manage the team dynamics to keep everybody moving forward and not fragmenting.

 

What aspects of the job were particularly appealing to you?

One of the parts of being a division chair that I have really enjoyed is being engaged with something that's bigger than my own research. And there's definitely a lot of that on 2020. It's a huge undertaking. There are not many science projects of this scale to be associated closely with, so this just seemed like a really good opportunity.

The kinds of questions that 2020 is going after—they're really big questions. You could never answer them on your own. The key objective is about life—is there or was there ever life on Mars, and more broadly what does its presence or absence mean about the frequency and evolution of life within the universe? There's no way you could answer these questions on Earth. The simple reason for that is that Mars is covered by rocks that are of the era in which, at least on our planet, we believe life was evolving. There are almost no rocks left of that age on the earth, and the ones that are left have been really badly beaten up. So Mars is a place where you really stand a chance of answering these questions in a way that you probably can't anywhere else.

It's not the kind of science I'm usually associated with, but the mission is trying to address truly profound scientific questions.

 

As you said, space has not been the focus of your research for most of your career. Can you talk a bit about how a terrestrial geochemist like yourself wound up in this role on a Mars mission?

Several years ago, I participated in a workshop about quantifying martian stratigraphy, which was hosted by the Keck Institute for Space Studies [KISS]. One of the topics that was discussed was geochronology—the dating of rocks and other materials—on other planetary bodies, like Mars. This is important for establishing the history of a planet and is particularly challenging because it requires such exacting measurements. After interacting with some people who are now my JPL collaborators at the workshop, it seemed like we might be able to do something special that would help solve this problem. And we got support from KISS to do a follow-on study.

As I was getting deeper and deeper into thinking about how we could do this on Mars, John Grotzinger (the Fletcher Jones Professor of Geology at Caltech and project scientist for MSL) was conducting the landing-site workshops for MSL. He would say things like, "Oh, it would be really great if we could date this." And we'd agree. Then there was a call for participating scientists on MSL. I had no background whatsoever in this, but I knew there was a mass spectrometer on Curiosity. That's one of the analytical instruments we need to make these dating measurements because it allows us to determine the relative abundances of various isotopes in a sample. Since those isotopes are produced at known rates, their abundances tell us something about the age of the sample. So I wrote a proposal basically saying let's see if we can make Curiosity's mass spectrometer work for this purpose. And it did.

 

What do you think led to your selection as project scientist?

Although I don't have a long track record in studying Mars, this mission is possibly the first step in bringing samples back to Earth. In order to do that, you have to answer a lot of questions related to geochemistry, which is my specialty. The geochemistry community is not ordinarily thinking about rocks coming back from Mars. I happen to have enough crossover between what I know about Mars from the work I just described and my background from working in geochemistry labs, especially those working with the type of very small samples we might get back from Mars, to be a good fit.

 

Given Curiosity's success on Mars, why is it important and exciting for us to be sending another rover to the Red Planet?

One thing to realize is that the surface of Mars is more or less equivalent in size to the entire continental surface area of the earth, and we've been to just a few points. It's naturally tempting to look at the few places we have been on Mars and draw grand conclusions from them, but you could imagine if you landed in the middle of the Sahara Desert and studied the earth, you would come up with different answers than if you landed in the Amazon, for example. So that's part of it.

But the big thing that distinguishes Mars 2020 is the fact that we are preparing this cache, which is the first step in a process that will hopefully bring samples back to Earth some day. It's very clear that from the science community's point of view, this is a critical motivation for this mission.

 

How has the experience been working on the mission thus far?

I enjoy it very much. It's extremely different to go from a lab group of two or three people to a project that, at the end of the day, is going to have spent $1.5 billion over the next seven or eight years. It's a completely different scale of operation.

I find it really fascinating to see how everything works. I've spent my entire career among scientists. Suddenly transitioning and working with engineers is interesting because their approach and style is completely different. But they're all extremely good at what they do.

It's a lot of fun to work with these people and to face completely new and unexpected challenges. You never know what new thing is going to pop up.

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Kimm Fesenmaier
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Hiroo Kanamori Receives William Bowie Medal from American Geophysical Union

Caltech's John E. and Hazel S. Smits Professor of Geophysics, Emeritus, Hiroo Kanamori, will be receiving the highest award of the American Geophysical Union (AGU), the William Bowie Medal, at this year's AGU meeting on December 17, 2014, in San Francisco.

The medal was established in 1939 to honor William Bowie, the first president of the AGU (1920–1922), and is given in recognition for "outstanding contributions to fundamental geophysics and for unselfish cooperation in research."

Kanamori retired from Caltech in 2005 after 33 years as a professor of geophysics. He was the director of the Seismological Laboratory from 1990 to 1998.

Over his career, Kanamori pursued multiple research questions on the physics and diversity of earthquakes, from slow tsunami earthquakes and megathrust earthquakes to large outer-rise and intra-plate earthquakes. Recognizing both the deterministic and chaotic features of earthquakes, he contributed to the development of effective real-time methods for hazard mitigation.

"I have never put myself in the category of distinguished AGU scientists," says Kanamori, "so this honor is overwhelming. I hope this will encourage my colleagues who share my scientific interests and philosophy."

Other Caltech faculty who have been awarded the William Bowie Medal include Gerald Wasserburg, the John D. MacArthur Professor of Geology and Geophysics, Emeritus (2008); Don Anderson, the Eleanor and John R. McMillan Professor of Geophysics, Emeritus (1991); and several former Caltech faculty members, including Eugene Shoemaker (1996), Frank Press (1979), Hugo Benioff (1965), and Beno Gutenberg (1953).

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Cynthia Eller
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Caltech-Led Team Develops a Geothermometer for Methane Formation

Methane is a simple molecule consisting of just one carbon atom bound to four hydrogen atoms. But that simplicity belies the complex role the molecule plays on Earth—it is an important greenhouse gas, is chemically active in the atmosphere, is used in many ecosystems as a kind of metabolic currency, and is the main component of natural gas, which is an energy source.

Methane also poses a complex scientific challenge: it forms through a number of different biological and nonbiological processes under a wide range of conditions. For example, microbes that live in cows' stomachs make it; it forms by thermal breakdown of buried organic matter; and it is released by hot hydrothermal vents on the sea floor. And, unlike many other, more structurally complex molecules, simply knowing its chemical formula does not necessarily reveal how it formed. Therefore, it can be difficult to know where a sample of methane actually came from.

But now a team of scientists led by Caltech geochemist John M. Eiler has developed a new technique that can, for the first time, determine the temperature at which a natural methane sample formed. Since methane produced biologically in nature forms below about 80°C, and methane created through the thermal breakdown of more complex organic matter forms at higher temperatures (reaching 160°C–200°C, depending on the depth of formation), this determination can aid in figuring out how and where the gas formed.

A paper describing the new technique and its first applications as a geothermometer appears in a special section about natural gas in the current issue of the journal Science. Former Caltech graduate student Daniel A. Stolper (PhD '14) is the lead author on the paper.

"Everyone who looks at methane sees problems, sees questions, and all of these will be answered through basic understanding of its formation, its storage, its chemical pathways," says Eiler, the Robert P. Sharp Professor of Geology and professor of geochemistry at Caltech.

"The issue with many natural gas deposits is that where you find them—where you go into the ground and drill for the methane—is not where the gas was created. Many of the gases we're dealing with have moved," says Stolper. "In making these measurements of temperature, we are able to really, for the first time, say in an independent way, 'We know the temperature, and thus the environment where this methane was formed.'"

Eiler's group determines the sources and formation conditions of materials by looking at the distribution of heavy isotopes—species of atoms that have extra neutrons in their nuclei and therefore have different chemistry. For example, the most abundant form of carbon is carbon-12, which has six protons and six neutrons in its nucleus. However, about 1 percent of all carbon possesses an extra neutron, which makes carbon-13. Chemicals compete for these heavy isotopes because they slow molecular motions, making molecules more stable. But these isotopes are also very rare, so there is a chemical tug-of-war between molecules, which ends up concentrating the isotopes in the molecules that benefit most from their stabilizing effects. Similarly, the heavy isotopes like to bind, or "clump," with each other, meaning that there will be an excess of molecules containing two or more of the isotopes compared to molecules containing just one. This clumping effect is strong at low temperatures and diminishes at higher temperatures. Therefore, determining how many of the molecules in a sample contain heavy isotopes clumped together can tell you something about the temperature at which the sample formed.

Eiler's group has previously used such a "clumped isotope" technique to determine the body temperatures of dinosaurs, ground temperatures in ancient East Africa, and surface temperatures of early Mars. Those analyses looked at the clumping of carbon-13 and oxygen-18 in various minerals. In the new work, Eiler and his colleagues were able to examine the clumping of carbon-13 and deuterium (hydrogen-2).

The key enabling technology was a new mass spectrometer that the team designed in collaboration with Thermo Fisher, mixing and matching existing technologies to piece together a new platform. The prototype spectrometer, the Thermo IRMS 253 Ultra, is equipped to analyze samples in a way that measures the abundances of several rare versions, or isotopologues, of the methane molecule, including two "clumped isotope" species: 13CH3D, which has both a carbon-13 atom and a deuterium atom, and 12CH2D2, which includes two deuterium atoms.

Using the new spectrometer, the researchers first tested gases they made in the laboratory to make sure the method returned the correct formation temperatures.

They then moved on to analyze samples taken from environments where much is known about the conditions under which methane likely formed. For example, sometimes when methane forms in shale, an impermeable rock, it is trapped and stored, so that it cannot migrate from its point of origin. In such cases, detailed knowledge of the temperature history of the rock constrains the possible formation temperature of methane in that rock. Eiler and Stolper analyzed samples of methane from the Haynesville Shale, located in parts of Arkansas, Texas, and Louisiana, where the shale is not thought to have moved much after methane generation. And indeed, the clumped isotope technique returned a range of temperatures (169°C–207°C) that correspond well with current reservoir temperatures (163°C–190°C). The method was also spot-on for methane collected from gas that formed as a product of oil-eating bugs living on top of oil reserves in the Gulf of Mexico. It returned temperatures of 34°C and 48°C plus or minus 8°C for those samples, and the known temperatures of the sampling locations were 42°C and 48°C, respectively.

To validate further the new technique, the researchers next looked at methane from the Marcellus Shale, a formation beneath much of the Appalachian basin, where the gas-trapping rock is known to have formed at high temperature before being uplifted into a cooler environment. The scientists wanted to be sure that the methane did not reset to the colder temperature after formation. Using their clumped isotope technique, the researchers verified this, returning a high formation temperature.

"It must be that once the methane exists and is stable, it's a fossil remnant of what its formation environment was like," Eiler says. "It only remembers where it formed."

An important application of the technique is suggested by the group's measurements of methane from the Antrim Shale in Michigan, where groundwater contains both biologically and thermally produced methane. Clumped isotope temperatures returned for samples from the area clearly revealed the different origins of the gases, hitting about 40°C for a biologically produced sample and about 115°C for a sample involving a mix of biologically and thermally produced methane.

"There are many cases where it is unclear whether methane in a sample of groundwater is the product of subsurface biological communities or has leaked from petroleum-forming systems," says Eiler. "Our results from the Antrim Shale indicate that this clumped isotope technique will be useful for distinguishing between these possible sources."

One final example, from the Potiguar Basin in Brazil, demonstrates another way the new method will serve geologists. In this case the methane was dissolved in oil and had been free to migrate from its original location. The researchers initially thought there was a problem with their analysis because the temperature they returned was much higher than the known temperature of the oil. However, recent evidence from drill core rocks from the region shows that the deepest parts of the system actually got very hot millions of years ago. This has led to a new interpretation suggesting that the methane gas originated deep in the system at high temperatures and then percolated up and mixed into the oil.

"This shows that our new technique is not just a geothermometer for methane formation," says Stolper. "It's also something you can use to think about the geology of the system."

The paper is titled "Formation temperatures of thermogenic and biogenic methane." Along with Eiler and Stolper, additional coauthors are Alex L. Sessions, professor of geobiology at Caltech; Michael Lawson and Cara L. Davis of ExxonMobil Upstream Research Company; Alexandre A. Ferreira and Eugenio V. Santos Neto of Petrobas Research and Development Center; Geoffrey S. Ellis and Michael D. Lewan of the U.S. Geological Survey in Denver; Anna M. Martini of Amherst College; Yongchun Tang of the Power, Environmental, and Energy Research Institute in Covina, California; and Martin Schoell of GasConsult International Inc. in Berkeley, California. The work was supported by the National Science Foundation, Petrobras, and ExxonMobil.

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Kimm Fesenmaier
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Geothermometer for Methane Formation
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